Mysterious metal ID help

[Evan]

I have several good sized shafts of stainless steel that were given to me by Tryp when he moved east. I would like to narrow down what sort of SS they are. I have done a few tests but need an interpretation of certain results.

The material is very non-magnetic. However, it exhibits an anomalous response to work hardening. I have beaten the daylights out of one end of a test sample and the beaten end is much less magnetic than the unworked end. The is the opposite of what is expected for 300 series austenitic stainless steel, which is likely the alloy group of this material. Work hardening of 300 series SS normally produces an increase in magnetic attraction, not a decrease.

The material machines and cuts beautifully with a fine finish using HSS or carbide tooling. It cuts very easily with a horizontal bandsaw leaving a very clean cut and with no sign of work hardening

Bandsaw cut: Please ignore rust stains, they are just contamination of the surface by contact with rusty mild steel. Shaft is about 1.5" OD.



One end of the shaft is was drilled and tapped leaving a relatively thin wall. I used a small hand sledge as seen in the background to hammer it with a dozen heavy blows. Instead of plastic deformation the material exhibits brittle failure with very little plastic yield.

Example 1:



Example 2:



Any ideas what alloy and/or chemical exposure would produce such a result?

[Peter N]

Perhaps it could a low-nickel stainless, such as a 200 series?

Very non-magnetic, but the anomaly appears to be in the work hardening behaviour.
The 200 series will apparantly work harden more than the 300 series, and are not suitable for drawing due to more fracture potential.

So one aspect seems compatible with your tests, but the other doesn't.

Peter

[Evan]

The magnetic anomaly is significant. The bandsaw cut end will pull a small supermagnet off my hand with a 5mm gap. The magnet won't even stick to the fractured end and just barely to intact metal just below it.

[Doc Nickel]

Potentially Monel. I have two large boat prop shafts made of the stuff, and have used small pieces.

I can attest to the work hardening with heat (I was forced to use a chop saw, it was either that or a hand hacksaw through a 1-1/2" shaft) but it turned with both HSS and carbide tooling as expected for any other 300 series stainless.

I can't say how it would deform under beatings like yours, though, as I've never beat on it.

Doc.

[Evan]

I can't say how it would deform under beatings like yours, though, as I've never beat on it.

Monel sounded promising until I checked that property. Monel has 48% elongation before break. This stuff is less than 10 percent.

[John Stevenson]

unwackiumnonmagneticium ?


.

[TECHSHOP]

Having no idea where the shaft has "come from", there are "medical equipment" alloys that are high in Cr, Ni, and Mo. That are magnetic or paramagnetic.

There also 17Cr-4Ni Precipitation Hardening stainless; this is used for things like papermill and food processing equipment, and might be a "more reasonable guess".

Also a lot of "parts" I have seen that where internally threaded stainless steel where sintured(sp) powder metal, and don't "bend" when "whacked".

The "known" stainless I have worked with the "300 series" and "18-8" types, but usually a repair was to unwackiumnonmagneticium, often used to make the arbors of circular saws.

[Evan]

often used to make the arbors of circular saws

Obviously the ones without magnetic brakes.

Tryp (Erik) used to work someplace dealing with harsh chemicals. That's why I asked about exposure to chemicals. Stainless steels are subject to chloride induced Stress Corrosion Cracking caused by exposure to compounds containing chlorine including sea water and bleach. I am wondering is this is an example (severe) of such exposure. I also wonder if such SCC might affect the magnetic properties of the material by producing separations between the magnetic domains at the crystal boundaries.

[aboard_epsilon]

That last picture looks like an old piece of galvanised pipe that has been stuck in the ground as a support for a tree for many years ...until you pulled it out and wellied the crap out of it .

maybe ....wrought iron and galvanised.

all the best......mark

[Evan]

maybe ....wrought iron and galvanised.

Definitely not. Here is what the part came from. The shaft had large bearings similar to the other shown. It was a part of some sort of chemical processing equipment.

[QSIMDO]

Looks suspiciously like the other end of the piece I caught smart-ass remarks about when I asked!

[Rusty Marlin]

Now that's funny!


Evan, my fist guess would have been Ni alloy of some sort, but not after seeing the fractured end, Ni just doesn't do that, or at least not the alloys I have used.

The way it shatters looks like a high chrome stainless like 13-8...

Any chance of making some test samples for tensile, shear, torsion, impact, crack propigation that could be taken to a local tech collage?

[Swarf&Sparks]

Living near a heavy industrial area, mates often bring me scrap of various exotics. The work hardening and magnetic behaviour sounds like a duplex, but that is bloody near impossible to machine

[tryp]

Interesting

Interesting find Evan. Very curious.

All of the shafting I salvaged came from water pumps, with the odd one that may have had contact at the impeller end with sodium chlorate and or sodium chloride brine solution with a high pH. All of the dichromate solutions and Hydrochloric/sulphuric acids were handled in mag drive sealed impeller pumps.

I was wishing I had some of that shafting recently while trying to kludge together a dedicated vertial overarm for my new mill (pictures coming soon)

I also cant wait to see what you are building now.

[Evan]

Any chance of making some test samples for tensile, shear, torsion, impact, crack propigation that could be taken to a local tech collage?

Unfortunately, no. Years ago when I serviced equipment at a local copper mine I could take samples there and have them analyzed in the assay department. I no longer have any connections there. As I have time I will do some more testing to try and find out what it is, mainly from curiosity.

Hi Erik. I certainly hope to see your new equipment. I'm happy to report the shaper is running fine. I just don't have enough time right now to do much with it. My son and his family are arriving here today and we shall be very occupied, especially with our 3 year old grandson.